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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_1410_Библиотеки_им_академика_М_И_Перельмана
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142 The ASCRS Manual of Colon and Rectal Surgery
Fig. 7.6. This image demonstrates a uT3N1 lesion. The tumor disrupts all layers
of the rectal wall, with extensions evident into the perirectal fat (A). A lymph
node (B) is identifi ed in the left posterior location within the mesorectum.
• Sonographically, there is loss of the normal hyperechoic interface between the tumor and adjacent organ (Fig. 7.7 ).
• Therapy of a T4 lesion usually requires preoperative radiation
and chemotherapy followed by surgical resection of the rectal
cancer and involved adjacent organ. The overall prognosis is
poor, with less than half of patients resected for cure.
• Preoperative radiation and chemoradiation therapy can shrink
the tumor for increased resectability and decreased local recurrence. ERUS provides the means to preoperatively identify those
lesions with T4 involvement to adequately plan the patient’s
treatment.
Nodal Involvement
• ERUS is able to detect metastatic lymph nodes in the mesorectum.
Unfortunately, the accuracy of detecting involved lymph nodes is
less than the accuracy in determining the depth of invasion.
• The accuracy of ERUS in detecting lymph node metastases
ranges from 50 to 88%.
• ERUS determination of metastatic lymph nodes is certainly
more accurate than clinical (digital) evaluation as well as other
imaging modalities including CT and conventional magnetic
7. Endoluminal Ultrasound 143
Fig. 7.7. This image identifi es a T4 lesion in the distal rectum and upper anal
canal extending to the vagina. The curved white line (A) seen anteriorly represents the examiner’s fi nger in the vagina, and the hypoechoic anterior tumor (B)
can be seen to extend into the vagina.
resonance imaging (MRI). However, phased array MRI and
endorectal coil MRI are comparable to ERUS in lymph node
assessment.
• Undetectable or benign-appearing lymph nodes are classifi ed
as uN0.
• Malignant-appearing lymph nodes are classifi ed as uN1.
• Normal, nonenlarged lymph nodes are usually not detectable
by ERUS.
• Infl amed, enlarged lymph nodes appear hyperechoic with irregular borders.
• Lymph nodes suspicious for malignancy include larger, round,
hypoechoic lymph nodes with an irregular contour. ERUS fi ndings consistent with metastatic lymph nodes are demonstrated
in Fig. 7.8 .
• Hypoechoic lymph nodes greater than 5 mm are highly suspicious for metastases. Involved lymph nodes are usually found
adjacent to the primary tumor or within the proximal mesorectum.
• Statistically, the incidence of metastatic disease increases as
lymph node size increases.
144 The ASCRS Manual of Colon and Rectal Surgery
Fig. 7.8. This image demonstrates a typical metastatic lymph node (A), which
is round and hypoechoic.
• Four nodal patterns are seen with differing probabilities of
being involved with metastatic disease:
– Nonvisible lymph nodes on ultrasound have a low prob-
ability of harboring lymph node metastases.
– Hyperechoic lymph nodes with nonsharply delineated
boundaries are more often benign resulting from infl ammatory changes.
– Hypoechoic lymph nodes larger than 5 mm are highly
suggestive of lymph node metastases.
– Mixed echogenic lymph nodes larger than 5 mm are dif-
fi cult to classify but should be considered malignant.
• Accurate lymph node staging of rectal cancers by ERUS relies
on the experience of the examiner.
• False-negative results are also problematic in interpreting nodal
involvement on ERUS. Lymph nodes harboring micrometastases
are diffi cult to detect. Grossly malignant lymph nodes may be
present outside the range of the ultrasound probe and remain
undetectable. This may be the case of lateral pelvic lymph
nodes such as the obturator nodes as well as those within the
mesorectum beyond the proximal extent of the rigid probe.
7. Endoluminal Ultrasound 145
Accuracy of Ultrasound in the Diagnosis of Rectal
Cancer
• The accuracy of ERUS for tumor depth of invasion has been
reported in the range of 69–94% (Table 7.2 ).
• Overstaging has been reported in approximately 10% of patients
and is believed to be the result of peritumoral infl ammation
beyond the leading edge of the tumor.
• Understaging for depth of wall invasion has been reported to
be approximately 5% and is considerably more serious than
overstaging because inadequate management may result.
• Detection of lymph node metastases with ERUS has been less
accurate, ranging from 61% to 83% in reported series (Table 7.2 ).
• There is a signifi cant learning curve associated with the performance and interpretation of ERUS. Accuracy rates have
been demonstrated to improve signifi cantly with experience.
Table 7.2. Accuracy of ERUS in the staging of rectal cancer.
Accuracy
(%)
Author Year n
Hildebrandt and Feifel 1985 25 92 n/a
Romano et al. 1985 23 87 n/a
Hildebrandt et al. 1986 76 88 74
Holdsworth et al. 1988 36 86 61
Beynon et al. 1989 100 93 83
Dershaw et al. 1990 32 75 72
Glaser et al. 1990 86 88 79
Glaser et al. 1990 110 94 80
Jochem et al. 1990 50 80 73
Milsom and Graffner 1990 52 83 83
Orrom et al. 1990 77 75 82
Katsura et al. 1992 112 92 n/a
Herzog et al. 1993 118 89 80
Sentovich et al. 1993 24 79 73
Deen et al. 1995 209 82 77
Adams et al. 1999 70 74 83
Garcia-Aguilar et al. 2002 545 69 64
Marusch et al. 2002 422 63 n/a
Manger and Stroh 2004 357 77
T stage
Accuracy
(%)
N stage
75
146 The ASCRS Manual of Colon and Rectal Surgery
ERUS is highly operator dependent and thus accuracy is
dependent on the experience and expertise of the examiner.
• Postbiopsy and postsurgical changes, hemorrhage, and bulky
or pedunculated tumors can cause changes in the ultrasound
image signifi cantly affecting the accuracy of the ERUS interpretation.
• The accuracy of ERUS after neoadjuvant therapy is decreased.
Radiation therapy can signifi cantly downstage tumors and may
in fact leave no residual tumor within the pathologic specimen.
In fact, up to 24% of patients treated with preoperative radiation therapy have a complete pathologic response with no evidence of residual tumor.
• Radiation therapy can cause tissue edema and fi brosis of the
rectal lesion making ERUS interpretation diffi cult. One cannot
accurately distinguish radiation-induced changes from residual
tumor. For these reasons, reevaluation of rectal lesions with
ERUS after radiation therapy is inaccurate, unreliable, and not
recommended.
Postoperative Follow-Up
• Even with newer adjuvant therapies available, surgical resection remains the best chance of cure for the patient with isolated local recurrence.
• When used in combination with a digital rectal examination
and endoscopic surveillance, ERUS may signifi cantly improve
the sensitivity of detecting recurrent lesions. ERUS may
improve the ability to diagnose recurrent neoplasm by as much
as 30%.
• Although local recurrence occurs intraluminally at the anastomosis, locally recurrent tumor usually occurs from extrarectal
tumor that invades through the rectum, often at the level of an
anastomosis.
• Recurrent tumor appears as a circumscribed hypoechoic lesion
in the para-anastomotic tissues with all or a portion of the
rectal wall intact on the inner, luminal aspect (Fig. 7.9 ).
• Because ERUS cannot establish that a lesion is malignant with
absolute certainty, a biopsy of suspicious lesions is recommended
to confi rm recurrent disease. Biopsies may be performed by
ultrasound-guided biopsy or computed tomography scan-guided
biopsy.
7. Endoluminal Ultrasound 147
Fig. 7.9. This image demonstrates a recurrent rectal cancer. It is located in the left
lateral rectal wall. Note the intact inner three lines (A) on the ultrasound image,
indicating no involvement of the mucosa or submucosa but an obvious abnormality
at the level of the muscularis propria (B), representing the recurrence.
B. Endoanal Ultrasound
• EAUS is useful in the evaluation of the anal canal in both
benign and malignant disease.
• The anal sphincter anatomy can be clearly identifi ed detecting
abnormalities in the external and/or internal sphincter.
• EAUS is routinely used in the evaluation of fecal incontinence
and may be particularly useful in the evaluation of complex
perianal abscesses and fi stulas.
• EAUS is also useful in the evaluation of anal canal neoplasms
accurately staging these lesions.
Equipment and Technique
• The equipment used for EAUS is similar to that used for
ERUS.
• In place of the latex balloon, a translucent plastic cap (B-K
type WA0453) is placed over the transducer to maintain contact
148 The ASCRS Manual of Colon and Rectal Surgery
with the anal canal. The plastic cap is again fi lled with water to
provide the acoustic medium.
• The examination technique for EAUS is similar to that of
ERUS.
• Certain instances of complex anorectal sepsis may be painful
and require examination under anesthesia to adequately image
the patient with EAUS.
Image Interpretation
• Normal anal canal anatomy is well visualized with EAUS.
• The ultrasonographic anatomy of the anal canal is generally
divided into three levels: the upper, mid, and distal anal canal.
Each level has a different appearance on EAUS.
• The upper anal canal is illustrated in Fig. 7.10 .The puborectalis
is an important landmark delineating the upper anal canal. The
puborectalis is imaged as a horseshoe-shaped mixed-echogenic
structure forming the lateral and posterior portion of the upper
anal canal.
• The mid anal canal is illustrated in Fig. 7.11 . Within the mid
anal canal, the internal anal sphincter is represented by a hypoechoic band surrounded by the hyperechoic external anal sphincter. Between the transducer and the internal anal sphincter is an
additional hyperechoic ring of variable thickness representing
the epithelial, hemorrhoidal, and submucosal tissues.
• Perineal body measurements can be made at the level of the
mid anal canal (Fig. 7.12 ).
• With the probe positioned within the mid anal canal, the right
index fi nger is placed within the vagina against the rectovaginal septum and ultrasound probe. The distance between the
hyperechoic ultrasound refl ection of the fi nger and the inner
aspect of the internal anal sphincter may be measured and represents the perineal body thickness.
• Normal measurements for perineal body thickness range from
10 to 15 mm, with a lower limit of normal considered to be
approximately 8 mm. This measurement is useful in the evaluation of women with fecal incontinence from anterior sphincter defects.
• The distal anal canal is illustrated in Fig. 7.13 . The distal anal
canal is defi ned as the point where the internal anal sphincter
is no longer seen. Only the hyperechoic external anal sphincter
and surrounding soft tissues are visualized.
7. Endoluminal Ultrasound 149
Fig. 7.10. This image represents the ultrasound appearance of the upper anal
canal at the level of the puborectalis, which can be seen as the hyperechoic
U-shaped structure seen posteriorly and laterally ( arrows ) in this image.
Fig. 7.11. This image depicts the characteristic appearance of the mid anal canal.
The circular hypoechoic structure represents the internal anal sphincter (A), surrounded by the thicker hyperechoic circumferential external anal sphincter (B).
150 The ASCRS Manual of Colon and Rectal Surgery
Fig. 7.12. This image depicts the technique used to measure the anterior perineal
body in a female patient. The examiner’s fi nger is placed in the vagina, and the
hyperechoic curvilinear structure (A) seen anteriorly delineates the examiner’s
fi nger. The two crosshatches between the examiner’s fi nger and the transducer
measure the thickness of the perineal body in this intact sphincter at the mid anal
canal level.
Evaluation of Fecal Incontinence
• EAUS has an important role in the evaluation of fecal incontinence, accurately delineating anal sphincter anatomy. Causes
of anal sphincter defects include obstetric injuries, anorectal
surgeries, traumatic injuries, and congenital abnormalities.
• Fecal incontinence is eight times more frequent in women, the
most common cause being obstetric trauma leading to injury of
the anal sphincter muscles or traction neuropathy involving the
pudendal nerve.
• Although anal sphincter injury identifi ed during delivery does
not lead to signifi cant deterioration in sphincter function immediately, it is suspected to lead to fecal incontinence in approximately 40% of women in long-term follow-up despite primary
sphincter repair.
• Patients may also develop delayed symptoms of incontinence
several years after an unrecognized sphincter injury.
7. Endoluminal Ultrasound 151
Fig. 7.13. This image represents the distal anal canal below the inferior level of
the internal sphincter, where only the hyperechoic circumferential fi bers of the
superfi cial external anal sphincter (A) are imaged.
• The introduction of EAUS has led to the recognition of unsuspected sphincter defects in asymptomatic, continent women
thought to have normal perineums.
• Traumatic sphincter disruption can frequently be associated
with a subsequent rectovaginal fi stula. These patients may
be anally continent but have symptoms of fecal incontinence
associated with the fi stula. Because these patients may have an
unrecognized anal sphincter defect, all patients with rectovaginal fi stula should undergo preoperative evaluation for occult
sphincter defects by EAUS.
• Local tissues are inadequate for endorectal advancement fl ap
repairs in patients with anal sphincter defects and these patients
should be treated by sphincteroplasty with levatoroplasty.
• EAUS has become the best modality to accurately demonstrate
the anatomy of the anal canal as well as anal sphincter defects
that contribute to fecal incontinence.
• Defects in the external anal sphincter usually appear hypoechoic, although some may appear hyperechoic or demonstrate
mixed echogenicity.
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